1. Field of the Invention
This invention relates generally to systems for powering low voltage high current electronics, and more particularly to, systems for powering low voltage high current electronic loads such as computer components.
2. Brief Description of the Prior Art
In prior art topologies for powering low voltage high current electronic loads low frequency techniques, generally 200-300 kHz, are used. To meet substantial changes in load demands a large output capacitance is becoming required. The cost of the capacitors becomes a substantial part of the power source cost and the location of these large capacitors close to the point of the load, which is usually the microprocessor, becomes difficult.
Some designers have attempted to solve these problems with switch mode power supplies that use phase shift regulation on the generator side of the power supply that transforms the energy of the primary DC source into AC energy. In other words phase shift regulation is used to control amount of energy generated by DC-to-AC inverter according the output load requirement. If the load requires it this AC energy can be transformed further into DC energy with help of the rectifier. In such a traditional architectures the rectifier plays a passive role and only transforms AC energy into DC without any regulation. The regulation capabilities of prior art topologies utilized in dc-dc converters are based upon controlling the amplitude of the sinusoidal AC voltage going to the input of the synchronous rectifier. Such a system is disclosed in U.S. Pat. No. 6,178,098 issued to Jen He et al. This patent teaches utilizing a feedback of a phase-shifted waveform to regulate the inverter of the power converter. A switching circuit phase shifts the waveform to increase or decrease the output of the inverter voltage into the rectifier of the dc converter. At the same time all prior art topologies using phase shift regulation operate at low frequency, generally 200-300 kHz, so they still require a large output capacitance.
A more advanced approach to providing a dc power conversion system which is both lower in cost than traditional topologies and performs a conversion from medium voltage dc to low voltage high current dc at the point of power consumption with high efficiency and fast regulation response is disclosed in the Co-pending Application Ser. No. 09/641,584 entitled, xe2x80x9cMultiple Power Converter System Using Combining Transformersxe2x80x9d assigned to the assignee of the instant application and incorporated herein by reference. This application discloses a plurality of power converters combined with coupled inductors, so arranged that the group of converters act together to produce a combined output that exhibits low voltage high current and fast regulation response. In other Co-pending Applications Ser. No. 09/534,641 entitled xe2x80x9cHigh Frequency Switch-mode DC Powered Computer System and Ser. No. 09/584,412 entitled xe2x80x9cSystem for Controlling the Delivery of Power to DC Computer Componentsxe2x80x9d both assigned to the assignee of the instant application and incorporated herein by reference, voltage regulation modules convert the sinusoidal power to low voltage high current power for computer loads in the first application and in the latter a high current secondary of a transformer located physically close to the load eliminates large currents being distributed to the converter input. As advanced as these designs are over traditional power converter topologies they too are based on controlling the amplitude of the sinusoidal AC voltage going into the synchronous rectifier.
It would be desirable if there were provided a system for powering electronics or computer components that were low in cost, small in size, had fast transient response, and provided a wide range of output voltages and currents.
There is provided by this invention a dc-dc power converter that functions in two stages. The first stage is a free running unregulated AC generator with either a sinusoidal or trapezoidal output voltage. The second stage is a synchronous rectifier working at the same switching frequency as the AC generator. The AC generator operates in zero-voltage switching mode, and the synchronous rectifier operates in both zero-voltage and zero-current modes which allows the use of frequency conversion rates up to 10 MHz. Changing the phase of commutation of the synchronous rectifier in reference to that of the AC generator controls the output power. Resonant sinusoidal and pulse gate drivers are used for both the AC generator and the synchronous rectifier. A low loss current combiner is used at the output of the system.